Obesity is also defined as a BMI (body mass index) over 30 kg/m2. Patients with a BMI between 25 and 29.9 are considered overweight, but not obese. See also diet and calories.

More than half of the U.S. population is overweight. But being obese is different from being overweight. An adult male is considered obese when his weight is 20% or more over the maximum desirable for their height; a woman is considered obese at 25% or more than this maximum weight. Anyone more than 100 pounds overweight is considered morbidly obese.

Rates of obesity are climbing. An ominous statistic is that the percentage of children and adolescents who are obese has doubled in the last 20 years.

The basic nutritional needs of most people are approximately 2,000 calories a day for women and 2,500 for men. However, people who are very active, such as professional athletes or manual laborers, may need 4,000 or more. Pregnant women and nursing mothers require about 300-500 more calories/day than women who are neither pregnant nor nursing.

The body cannot store protein or carbohydrates, so excess protein or carbohydrate intake is converted to fat for storage. One pound of fat represents about 3,500 excess calories.

Obesity increases a person's risk of illness and death due to diabetes, stroke, coronary artery disease, hypertension, high cholesterol, and kidney and gallbladder disorders. Obesity may increase the risk for some types of cancer. It is also a risk factor for the development of osteoarthritis and sleep apnea.

Genetic factors play some part in the development of obesity -- children of obese parents are 10 times more likely to be obese than children with parents of normal weight.

• Consumption of more food than the body can use
• Excess alcohol intake
• Sedentary lifestyle

See intentional weight loss.

To help prevent an increase in weight:

• Avoid the following:
  • excess alcohol consumption.
  • stress
  • depression
  • boredom and frustration
• Avoid a sedentary lifestyle by increasing your activity level:
  • Perform aerobic exercise for at least 30 minutes a day, 3 times a week
  • Increase physical activity in general by walking rather than driving.
  • Climb stairs rather than using an elevator or escalator.
• Reduce consumption of food that is high in fat and sugar.

For additional help in losing weight:

• Join a support group (see eating disorders - support group). Many people find it easier to follow a reduction diet and exercise program if they join a group of people with similar problems.
• Avoid over-the-counter drugs that claim to aid in weight loss -- most are ineffective, and some can be dangerous.

Also, be sure to set realistic goals for weight reduction. A loss of 1 to 2.5 pounds a week may seem slow, but losing weight too fast often does not work. Weight lost quickly is usually regained quickly.

• You are unable to lose weight on your own.

• Time pattern
  • Has there always (or since childhood) been a tendency to be heavy?
  • Has the person been slender until recently, and then begun to gain weight?
• Eating habits
  • Has diet changed recently?
  • Have eating habits changed?
  • What percent of the daily calories are from fat?
  • How many meals are eaten in a day? What type?
  • How many snacks? What type?
• Exercise habits
  • Has activity level changed?
  • Has there been a decrease in daily activity?
• Other factors
  • Is there an increase in emotional stress?
  • Have you increased your alcohol consumption?
  • What other symptoms are occurring at the same time?

Skin fold measurements may be taken to assess body composition. Blood studies to test endocrine function may be performed.

Treatment:
Medications are usually not recommended to aid intentional weight loss. They often cause harmful side effects or adverse reactions. At best, the drugs control appetite only for short time periods and don't help change eating habits.

Gastric outlet stapling may be indicated for the morbidly obese. Your primary care provider may want to refer you to a general surgeon for more information about this.